Comparisons of Relative Humidity Measurements from Sondes and CRIS/IASI Satellites

Relative humidity is an atmospheric property whose measurements are critical for a variety of research efforts including boundary layer studies, cloud processes, atmospheric chemistry, and severe weather prediction. Humidity measurements are routinely made by orbital instruments and in-situ radiosondes which may disagree or show relative bias due to changes in instrumentation, observing practices, processing algorithms, or noise.Since radiative transfer models that depend on these measurements are very sensitive to the amount and distribution of atmospheric water vapor, absolute accuracy is needed. Inter-comparison between satellite and in-situ sonde measurements are difficult because the regular 0Z and 12Z sonde launches are not favorably aligned with satellite overpasses. In an effort to improve the comparison, we have undertaken a radiosonde campaign synchronized with CRIS/IASI satellite instrument overpass times to directly compare remote and in-situ measurements of humidity. Satellite and sonde profiles will be compared over the course of the year to establish if systematic measurement differences exist and to determine if they are dependent on pressure and/or temperature or other atmospheric properties.